Exemplary embodiments of the present invention relate to an apparatus and method for containing gas in an airbag inflator and releasing the gas at a variable rate into an inflatable cushion. The inflator provides gas for the inflation of automotive airbags for the purpose of protecting vehicle occupants from injury in the event of a crash. Gas must be provided quickly for occupant protection in side impact crashes. For crashes involving vehicle rollover, inflation of the airbag is required for an extended period of time.
Today some vehicles are supplied with side airbag modules. A side airbag module comprises inflatable cushions or curtains that traverse a side portion of the vehicle when they are deployed in accordance with a predetermined activation event. Generally, the device is located along a side of the vehicle in an un-inflated state and upon activation deploys an inflatable curtain along a side portion of the vehicle. Side impact air bags or inflatable cushions are often mounted in close proximity to the vehicle's roof rail, doorframe or center pillars, or in some instances within the side door. Accordingly, the space or housing for the un-inflated airbag is compact and extends or traverses along the window area or frame, as the airbag cannot be installed in the areas comprising the window. Moreover, it is also desirable to have the inflatable cushion disposed behind a decorative trim portion of the vehicle's interior. Thus, the presence of the side airbag device is not observable to occupants when it is in its un-deployed state.
Substantial efforts have been directed to developing inflatable cushions or curtains having extended periods of inflation or in other words inflatable cushions that will retain their inflation gases for a period time after inflation. Some methods for providing this extended period of inflation is to minimize the inflation gas leakage by providing a one-piece-woven curtain airbag or by applying a sealant at the seams where the two sides of an inflatable cushion are sealed together. However, both of these methods are costly as they add additional manufacturing steps and methods.
Extended airbag inflation time may be achieved by slowly releasing gas stored in a secondary chamber (See U.S. Pat. No. 6,543,806 B1) and using higher viscosity gases (See U.S. Pat. No. 6,883,830 B2). A combination of these features provides both side impact and rollover protection with a single device (See U.S. Patent Publication No. 20080246260). The release rate of the gas must be controlled accordingly. A larger discharge opening is required for a high viscosity gas compared to the opening required for a low viscosity gas.
Accordingly, it is desirable to provide an airbag module capable of providing an inflatable cushion or curtain with an extended period of inflation and an apparatus and method for containing and releasing the inflation gas from the inflator.